The rail service here in the UK is often the brunt of jokes. If it’s not the wrong type of rain, or the leaves are laying on the tracks the wrong way then it’s some other seemingly ludicrous reason that the trains are delayed, or even cancelled. A recent study by scientists at the University of Lancaster suggest that even the solar wind might cause train signals to be incorrectly triggered with potentially disastrous consequences.
The solar wind has been responsible for numerous displays of northern lights over recent months. The fast moving electrically charged particles from the Sun rush toward the Earth and on arrival, cause the gas in our atmosphere to glow. The displays can be mesmerising and inspiring yet their impact is all too familiar with telecommunication failures and other satellite technology problems but it seems the impacts might also be felt a little closer to home, in rail systems around the world.
Circle of Light © Andreas Ettl. A stunning photograph of a vivid aurora over Skagsanden beach, Lofoten Islands, Norway. The mountain in the background is Hustinden, which the aurora appears to encircle.
The arrival of the particles causes magnetic disturbances in the atmosphere and it’s this that effects satellites. But they can also trigger geomagnetically induced currents (GICs) which interfere with electricity supply and transmission systems. The team from University of Lancaster which was led by Professor Jim Wild and researcher Cameron Patterson have modelled the flow of the GICs in rail systems, in particular, how they flow through the track circuits that are powered by overhead lines.
Two routes were modelled by the team; the Glasgow to Edinburgh line and the West Coast Main line. They investigated how the solar wind could induce GICs leading to signalling failures, and yes, apparently it is totally possible! Rail systems have red and green lights to signal the drivers to stop or go, obvious really. The signals are powered by electrical circuits between the rails.
Induced currents from solar wind it seems are capable of flipping a signal in either direction, in other words, switching the green light to the red (known as right-side failure) or the red light to the green (known as wrong-side failure). ‘Right-side’ failure is a fail safe scenario where the system fails safe, to red and trains stop. The other failure from red to green is far more dangerous.
The impact of solar wind is largely dependent on latitude and the UK based research revealed that solar wind or space weather events can be strong enough every few decades to trigger signal failures. Perhaps more worryingly is that it takes lower geoelectric field strength for the ‘wrong-side’ failures – and these are the switching from red to green scenario events, the more dangerous ones – than the ‘right-side’ failures.
Further analysis looked at more extreme space weather events, the sort that comes along once in a century. This showed that such an event could cause multiple signal changes across a route, in multiple directions and depending on the number of trains on the track! This is not all just conjecture, there is mounting evidence of just such an impact on signalling as far back as the 19th Century.
So next time you are planning a train journey, forget the leaves and the rain you can forget the type of snow too, just make sure you check out solar activity to see if it’s safe to make the journey.
Source : Rail industry urged to consider safety risks of space weather
link : https://www.lancaster.ac.uk/news/rail-industry-urged-to-consider-safety-risks-of-space-weather